Sounds about right, though it's rarity, as a percentage, is surely exactly the same as worn examples....how could it possibly be otherwise?
If I'm thinking straight, if the percentage of EF+ examples in the total extant population is larger than the percentage of 164a's in the total minted population,
then high grades may well be out there.
If it's lower, there won't likely be any.
Same as the 1903 open 3.